1. Field of the Invention
The present invention relates in general to an emulator for emulating a plurality of printers having respective different operation modes, and more particularly to such a printer emulator capable of detecting each of job units of a received batch of print data, and determining the operation mode for each job unit representative of a printing job, according to control codes included in the received print data, so that the printing job is effected in the determined mode.
2. Discussion of the Invention
Various types of printer are known, which operate according to a received batch of print data representative of texts to be printed. The print data include text data representative of alphabetic letters, numerals, symbols and other characters, and various control codes such as a code representative of the size of the characters, a code for commanding carriage return and line feeding movements, and a code for commanding pagination of the text. For improved printing quality and versatility, some printers are operable in two or more different modes, which are established by appropriate control codes.
For instance, a printer has a plurality of operation modes which correspond to respective combinations of printing speed (high-speed printing or low-speed printing), printing attitude (horizontal printing or vertical printing), and image resolution value (high-resolution or low-resolution, which is determined by the number of dots per inch in the case of a dot-matrix printer). The operation modes are selected by two or more control codes so-called "function-expanding control codes" (which follow an ESC code). Of course, the operation modes available on one type of printer may be different from those on another type of printer.
Therefore, suitable control codes should be included in the print data, so that printing jobs represented by respective job units of the print data are performed in the suitable operation modes. On the other hand, the print data used for a given type of printer should be written in a format that meets the operation modes available on that printer. Otherwise, the printing jobs represented by the print data cannot be performed in the intended operation modes.
In the light of the above inconvenience, a printer emulator is proposed as disclosed in laid-open Publication No. 63-216765 of unexamined Japanese Patent Application. The printer emulator disclosed therein is capable of emulating two or more types of printers, namely, capable of effecting printing jobs according to print data written in formats for other printers, by automatically detecting the operation mode of the received print data, on the basis of the control codes included in the print data. Thus, the batches of print data prepared for the other printers can be used on the printer emulator.
In the case where such a printer emulator is connected through an interface to a network which includes a plurality of computers or terminals, the printer emulator receives batches of print data from those external computers or terminals, which are written in different formats for different operation modes. In other words, a batch of print data received by the printer emulator may consist of two or more job units which represent individual printing jobs that should be performed in different modes desired by the operators of the external computers. In this case, however, there is a risk that the printer emulator performs all printing jobs in the same mode determined for the first commanded printing job, although the individual printing jobs commanded by the different external computers should be performed in respective different modes.